Undoing the damage

Aussie researchers turn CO2 gas back into solid coal

How would it affect the fight against climate change if we could pluck carbon dioxide right out of the sky? We might soon find out, thanks to researchers at Melbourne’s RMIT University. Dr. Torben Daeneke is part of a team that has found a cost-effective way of converting CO2 gas back into solid coal using liquid metals.

“While we can’t literally turn back time, turning carbon dioxide back into coal and burying it back in the ground is a bit like rewinding the emissions clock,” Daeneke said in a statement. “To date, CO2 has only been converted into a solid at extremely high temperatures, making it industrially unviable. By using liquid metals as a catalyst, we’ve shown it’s possible to turn the gas back into carbon at room temperature, in a process that’s efficient and scalable.”

Dr. Dorna Esrafilzadeh pioneered the technique, which dissolves gas in a beaker full of electrolyte liquid and a liquid metal alloy of gallium, indium, tin, and cerium. The metal is charged with an electrical current, converting the CO2 into solid carbon.

“A side benefit of the process is that the carbon can hold electrical charge, becoming a supercapacitor, so it could potentially be used as a component in future vehicles,” Esrafilzadeh said. “The process also produces synthetic fuel as a by-product, which could also have industrial applications.”

Until now, CO2 scrubbed from the air has been compressed into liquid and injecting into the ground, where the potential for leakage makes it a less than ideal solution. Conversion to solid was possible, but only at extremely high temperatures. The liquid metal catalyst solves that problem. Theoretically, the reformed coal could be reused as a fuel source. Daeneke said that even as we turn to green and renewable energy alternatives, there will likely still be a need to clean CO2 from the atmosphere to stabilise the climate.

“We don’t see any fundamental reasons why this cannot be upscaled and rolled out on a mass scale,” Daeneke said. “We are working at the moment on upscaling and designing prototype devices and reactors to do this in the most efficient and cost-effective way.”